There's not much you need to know about this one beyond the idea—as you can see, the execution is dead simple. Just attach a binder clip to your keychain, cut up some notecards, and you're good to go. This picture was uploaded to Flickr years ago, but we had never seen or featured it. In fact, we just stumbled onto it by chance while doing a little Flickr searching yesterday. Still, we love it. Nice work, kadavy!